A technology for cutting a long base material sheet to manufacture a plurality of rectangular unit pieces having a relatively small size has been adopted in various fields. For example, a base material sheet having a specific width and a long length is repeatedly cut by a cutting frame to simultaneously manufacture a plurality of rectangular unit pieces though a one-time cutting process.
Meanwhile, the size (width) of the base material sheet is specified, whereas the size of the rectangular unit pieces may vary as needed, due to various factors, such as the limitation of base material sheet suppliers, the efficiency aspect of the manufacturing process, the fluctuation in demand of rectangular unit pieces, etc. At this time, the cutting efficiency greatly varies depending upon how the cutting process is carried out. The low cutting efficiency increases the amount of scrap, produced from the base material sheet, which will be disposed of after the cutting process with the result that, eventually, the manufacturing costs of the rectangular unit pieces increase.
In a case in which the size (width and length) of a base material sheet is in constant proportion to the size (length and width) of rectangular unit pieces, it is possible to minimize the cutting loss by sequentially arranging the rectangular unit pieces such that the rectangular unit pieces are brought into contact with one another at positions having such constant proportion. In a case in which such constant proportion is not formed, however, the cutting loss may vary depending upon the array structure of the rectangular unit pieces. Furthermore, when the rectangular unit pieces are to be cut while the array of the rectangular unit pieces is changed according to optical directivity of the base material sheet, a large amount of scrap is inevitably produced.
When cutting base material sheet to manufacture a plurality of desired rectangular unit pieces based on the size of the base material sheet, therefore, a method of increasing the cutting rate of the base material sheet is very important in the aspect related to the manufacturing costs of the rectangular unit pieces.
The cutting rate of the base material sheet may vary typically depending upon the condition of the cutting process, the structure of the cutting frame, etc. That is, it is possible to achieve high cutting efficiency through the working condition to maximize the utilization of the base material sheet in the cutting process, the array structure in which cutters for cutting base material sheet to manufacture rectangular unit pieces are optimally arranged on the base material sheet, etc.
In order to cut the base material sheet according to optical directivity of the base material sheet to manufacture rectangular unit pieces, there is generally used an array structure in which the cutters (for example, knives) are arranged on the cutting frame such that the rectangular unit pieces corresponding to the cutters are adjacent to one another.
In connection with this respect, FIGS. 2 and 3 are partial typical views showing the array structure of rectangular unit pieces corresponding to cutters of a conventional cutting frame. In addition, FIG. 1 is a typical view showing that rectangular unit pieces, manufactured using the conventional cutting frame, are applied to a real product. For the convenience of description, a base material sheet is illustrated to have a predetermined length.
Referring to FIGS. 2 and 3 together with FIG. 1, unit piece A 20 cut in a direction parallel to optical directivity 25 and unit piece B 30 cut in a direction perpendicular to optical directivity 35 are arranged such that the optical directivity 25 and the optical directivity 35 are perpendicular to each other when the unit piece A 20 and the unit piece B 30 are applied to a product. Consequently, the rectangular unit pieces 20 and 30 are arranged according to optical directivity 15 of base material sheets 150 and 160.
Referring to FIG. 2, the rectangular unit pieces 20 are arranged on the base material sheet 150 to manufacture unit pieces A 20 having optical directivity 25 parallel to the optical directivity 15 of the base material sheet 150. Since the width W of the base material sheet 150 is not in constant proportion to the width of the rectangular unit pieces 20, however, cutting loss equivalent to the remaining portion (W3×L0) after cutting occurs.
Referring to FIG. 3, the rectangular unit pieces 30 are arranged on the base material sheet 150 to manufacture unit pieces B 30 having optical directivity 35 perpendicular to the optical directivity 15 of the base material sheet 160. Since the width W of the base material sheet 160 is not in constant proportion to the length of the rectangular unit pieces 30, however, cutting loss equivalent to the remaining portion (W4×L0) after cutting occurs.
Furthermore, two or more kinds of rectangular unit pieces having different optical directivities are manufactured from base material sheets having different constituents according to the optical directivities. For this reason, different kinds of rectangular unit pieces cannot be arranged on the same base material sheet to utilize the remaining portion after cutting.
Therefore, an array structure of unit pieces having higher cutting efficiency than the array structures of the unit pieces shown in FIGS. 2 and 2 and a manufacturing method based thereupon will reduce cutting loss and thus lower manufacturing costs of products. Improvement of cutting efficiency is more serious when base material sheets are expensive and/or rectangular unit pieces are mass-produced.